In recent years, the price of the petrochemical fuel is rising, and the power generation from the petrochemical fuel will result in the greenhouse effect and ruin the ecology and the environment. Therefore, a variety of countries one after another seek the alternative energy sources without ruining the environment of the earth. The regenerative energy source is undoubtedly one of the best choices in the alternative energy sources. For instance, the regenerative energy source includes the wind energy, the solar energy, the ocean energy, the hydraulic energy, and so forth. The ocean energy includes types of the tidal energy, the wave energy, the electrical energy of the temperature difference, the offshore wind energy, and so forth.
In recent years, employing the offshore wind farm becomes the new development trend in the field of the wind power generation. The wind power generation system having this type includes a wind tower, which is constructed on the seabed or on the buoyancy foundation support. The wind power generation system utilizes the steady wind energy on the sea to generate the electrical power. The wind tower occupies no land. Therefore, a plurality of wind power generators established at sea can form an offshore wind farm. The power generated by the offshore wind farm should be transmitted to the shore through a step-up transformer and a submarine cable for a further use.
Hughes et al disclose that a doubly-fed induction generator with a configured wind farm has a property similar to that of a synchronous generator, and has the ability to keep a system frequency. Wu et al use a particle swarm optimization to analyze a controller parameter of a doubly-fed induction generator so as to accomplish an optimum scheduling of a power generation system by an optimized controller parameter.  et al disclose that a reactive power of a doubly-fed induction generator is controlled to improve the output power quality of the doubly-fed induction generator and increase the stability thereof. Narayanan et al extend a hunting-network method to an induction generator mode to combine a Wells turbine with an induction generator.
Rao et al introduce a wave power generation system employing a Wells turbine. Murthy et al uses the Matlab/Simulink software to simulate an induction generator set driven by a Wells turbine so as to obtain a property of a higher output power. Wang et al accomplish a dynamic simulation and a dynamic stability analysis of a steady-state performance of a wave power generation system, and disclose that stator windings of an induction generator are connected to a power network through a step-up transformer and a transmission line. Merkhouf et al introduce a design concept of a variable frequency transformer, and disclose that a high-voltage DC transmission system can be replaced with the variable frequency transformer for controlling a power flow. Truman et al disclose a property of a DC driving motor that a variable frequency transformer needs using. Marken et al disclose that variable frequency transformers are respectively added into a plurality of different systems, and research the possibility that a variable frequency transformer is added to a current or future power network. Li et al use a variable-speed flywheel to serve as a multifunction flexible power conditioner, which has a better compensation effect. Andrade et al provide a configuration of a flywheel energy-storage system, and test a compensation effect resulting from a load variation when a flywheel energy-storage system is connected to a commercial electric supply. Thelen et al use a high-speed induction motor and a switching converter to serve as a transmission interface unit between a flywheel and a mixed power system. Gimuca et al provide a direct torque control method to control a flywheel energy-storage system having a dominant component of an induction machine, and match the flywheel energy-storage system with a variable-speed wind turbine generator to make a simulation.
Feltes et al disclose that: a voltage source converter and a high-voltage DC transmission system are applied to a wind farm, and the high-voltage DC transmission system is connected with a power network in parallel; and when the high-voltage power network has a fault, a control method is used to further stabilize the system.
Prabhua et al disclose that a high-voltage DC transmission system associated with a voltage source converter is connected to a power network, and an eigenvalue analysis in the frequency domain and a dynamic simulation analysis in the time domain are accomplished.
Muyeen et al use the PSCAD/EMTDC software to simulate an offshore wind farm formed by a permanent-magnet synchronous generator driven by a variable-speed wind turbine. Wang et al disclose a superconducting-magnetic energy-storage system having a control structure, the control structure is connected to a commercial electric supply, and the system is connected to a parallel offshore wind farm, thereby accomplishing a power flow control and improving a system damping control.
Please refer to FIG. 1, which is a schematic diagram showing a conventional wind power generator. In the Taiwanese issued utility model patent with No. M281076, an offshore wind power generation device 10 on the sea is provided. The offshore wind power generation device 10 includes a floating plate 11 and a wind power generator 12. The floating plate 11 can cause the offshore wind power generation device 10 to be positioned and float on the water. The wind power generator 12 is fixed on the floating plate 11, so that the natural wind force blows to move the blades 121 of the wind power generator 12 and causes the power generation unit inside the wind power generator 12 to be able to generate a power for supply.
The wave power generation is one of important develops in the ocean energy research, and utilizes a wave energy to generate an electrical power. The wave energy is converted into electrical power through a specific power generation device. The electrical power is transmitted through a step-up transformer and a submarine cable for a further use. The Wells turbine belongs to a type of a wave power generation device, and the blades of the Wells turbine are specifically designed, so that the blades are rotated in a single direction no matter the wave moves forward or backward.
Whether the wave power generation or the wind power generation is implemented, the power transmission, the power integration and the power control are necessary. Furthermore, there is the demand to provide a system for integrating a wind power generation with a wave power generation.